This invention relates generally to a machine for rebuilding worn tractor roller assemblies by depositing hard metal on the rim of the assembly while the rotor assembly is cooled by circulating coolant therethrough.
In track laying tractors, the upper span of the track is supported by roller assemblies while the tractor is supported on the lower ground engaging span of the track by roller assemblies. The roller assemblies typically include a rim which engages the track and is rotatably supported by an internal roller structure. Lubricant passages are formed in and between the interior structure and the rim. The passages are normally filled with lubricant and the structure sealed to provide a durable structure. The track roller and tracks are subjected to considerable wear because of the grinding action of the ground over which the tractor is operated. The exterior of the rim wears long before there is any wear of the internal structure of the roller.
It has become common practice to rebuild the exterior of the rim by applying a hard surface of metal by welding. Early machines for this purpose required that the roller be disassembled and the rim rebuilt by welding. In order to prevent overheating of the rim, intermittent welding operations were carried out, or the rim was submerged in water. Both of these processes are unsatisfactory because of the time consumed in the welding operaton and the time reqired to disassemble and reassemble the track roller assembly.
More recently, machines have been provided which permit rebuilding of the assembled rollers. Furthermore, these machines have included probes which are inserted into the roller circulated to circulate coolant through the lubricant passages to maintain the roller at suitable safe temperatures during the welding operations. This permits continuous welding of the roller without damage to the lubricant seals or warping and cracking of the metal. Typical machines of this type are described in U.S. Pat. Nos. 3,514,568; 3,596,041; and 3,895,209.
Such prior art systems have not provided for control of the coolant temperature whereby to maintain the roller at optimum temperature during the welding operation. Furthermore, upon completion of the welding operation, there is a waiting period for the roller assembly to cool down before the coolant supply can be disconnected. During this time the machine is idle. If, on the other hand, the coolant is disconnected prematurely, severe stresses are set up in the roller assembly which often lead to distortion or cracking of the metal parts of the assembly and damage to the roller seals.